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tuned visa engine
http://www.international2cvfriends.com/forum/viewtopic.php?f=7&t=5556		 Page 1 of 2
Author:  Rusty [ February 18th, 2015, 4:53 pm ]
Post subject:  tuned visa engine
For my Pick up I have been thinking to assemble a tuned visa engine.

I have almost everything on stock, my idea is the following:

-V06-630 bottom (fasted standard camshaft)
-V06-644 Cylinders (high compression) got a new old stock set of pistons and some new production pistons!
-1-2-spark ignition
-double SU HS2 carburetor (32 mm each)
-Sensorflange with gauges to see what is happening
-lambda sensor with gauge to monitor the fuel mixture
-first I will put a long ratio gearbox behind it, and at a later stage change it to an AMI super one.

I hope to get about 45 hp, couple of years ago with standard V06-644 engine, original visa carb and turbotube I got 34 hp (measured at the wheels)

For now I’ll put this assembly in my dyane to test, adjust, tweak and tune, then afterwards I can easily transfer it to the Pickup.

Gathered all the main parts last weekend, my lambda sensor and controller came in last week, waiting for the gauges to arrive from the ‘far east’

Just figuring out where to put the carbs, above the brake calipers, or above the starter motor?

Image

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new goodies :)

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Does anyone know of anyone putting 2 SU HS2 carbs on a 2 cil boxer? I know many have tried (and succeeded) with other types of carbs, but the neat thing of these SU ones is that they are ‘constant velocity’ carbs, which should be a big advantage. They came of a 70’s Mini cooper by the way so should be widely available.
greetzzzzzzzz

Rusty
Author:  Sean [ February 18th, 2015, 8:19 pm ]
Post subject:  Re: tuned visa engine
Try the "citroen specials club" ( Ken'll point you in the right direction), there was the bloke on here who was convinced that those rich running carbs cured all and had made lots of adapters

It might be worth working out how much flow a single carb sitting on a single cylinder is going to handle and how it behaves.

Im not a fan of SUs came from growing up with BL minis and other A seriese engines. Saab also used similar with Stromberg and that, on a 99, made your eyes water at the fuel pump
Author:  ChrisW [ February 19th, 2015, 8:50 pm ]
Post subject:  Re: tuned visa engine
I used amal carbs down below the exhaust exchange units. I used an old manifold, cut it and then used the RH inlet pipe on the LH side and the LH pipe on the RH side. This put the carb in just the right place. You can see it on the - your A series - 1976 Dyane 6.52 or something like that
Author:  Joolz [ February 20th, 2015, 2:04 am ]
Post subject:  Re: tuned visa engine
Not that I have any experience, but I hear one of the problems with the original carburetor is the long inlet manifold gives to much time for the fuel to condense on the walls. If it is possible is is best to have the carbs close to the head.
Author:  Sean [ February 20th, 2015, 8:55 am ]
Post subject:  Re: tuned visa engine
Joolz wrote:
Not that I have any experience, but I hear one of the problems with the original carburetor is the long inlet manifold gives to much time for the fuel to condense on the walls. If it is possible is is best to have the carbs close to the head.


yup and the harmonics it produces

remember putting 2 carbs on a 2cyl engine will reduce the volume going through it, a carb originally feeding 4 cylinders will barely get off its stops feeding a 300 single Bigger carb doesnt make more power
Author:  Rusty [ February 20th, 2015, 9:20 am ]
Post subject:  Re: tuned visa engine
Thnx for all the answers and thinking!


I'm not sure yet where to place the carbs, short manifolds will give a lot of low torque, long ones more high torque, that is why i would like them as long as possible. will mostly run the car in nice weather, so condensation is not directly one of my worries.

there is a kitcarguy here in the Netherlands who put a pair of 30 mm Dellortho's on a visa engine, with short manifolds. he got so much torque out of it, his front end got completely messed up (bearings, kingpins drive shafts e.t.c.) he even got wheel spin in 3rd gear!!!

If this works out, and makes enough power I can always 'change' to fuel injection, the price of such a setup holds me back for now. hopefully LPGO will get his 12-spark to extended to 12- squirt-spark :)

I also have the original mini manifold, this will use the 2 carbs partially at the same time. not sure yet if this is the way to go or not, may be good for the 'harmonics' in the setup.

1 stoke of a 600cc 2 cilinder engine, so 300 cc per side is comparable to a 'normal' 4 cilinder engine of 1200 cc! you just have not the harmonics; constan flow as you would have in a 4 cilinder.. many things to think of...

If anyone has got some more information about the guy that tried a pair of SU's on a 2cv, I would be very grateful! couldn't find anything on the 2cvspecials club yet.

greetzzzzzzzzzzzz

Rusty
Author:  lpgo [ February 20th, 2015, 1:27 pm ]
Post subject:  Re: tuned visa engine
Rusty, just try it, what do you have to loose, if it doesn't work, put it asside, if it works leave it as it is... I would also try to make them as long as possible, sounds good to me..

Looking at my beamer running at 2 2cv carbs, it runs suprisingly well (after I checked the valves and came to the conclusion that 1 exhaustvalve was always open (it had no play at all) :oops: )..

I think it will work well an if you don't have enough backpressure you can maybee connect both pipes together with a crosspipe.... But my feeling is you don;t need that....

Using a bigger carb then neccecery works well, the only problem is it will be more of an on and off switch then a smooth operating carb....

Also the petrol to wall thing isn't a problem. Mostly this is only a problem when hitting the acc. pedal. You probably need more acceleration enrichment then with a short inletmanifold..
Ones the engine is running on (a sort of ) stable rpm this will be no issue... petrol which will settle down must come off also..

Another trick would be to heat the inletmanifolds just like the Original 2cv inletmanifold is heated too.

I've heated my inletmanifolds at my Beamer too.. this also prevents the petrol to wall effect.. (i've welded some sheet metal between exhaustpipe and inletmanifold... It prevents also the carb from freezing in the winter....

Heres something about the wall wetting...

http://www.megamanual.com/ms2/xtau.htm
Author:  Joolz [ February 20th, 2015, 2:30 pm ]
Post subject:  Re: tuned visa engine
It is true that longer inlets can give more torque, but the length does need to be between the carb and the head. Placing the carb close to the head and using a long inlet trumpet has the same effect.
Author:  Rusty [ February 20th, 2015, 3:34 pm ]
Post subject:  Re: tuned visa engine
Ok, Cool, didn't know that! wanted to put a homemade airfilterbox on it, with turbotube of course! would this give problems with the SU's??

greetzzzzzzzz
Author:  lpgo [ February 20th, 2015, 4:13 pm ]
Post subject:  Re: tuned visa engine
Joolz wrote:
It is true that longer inlets can give more torque, but the length does need to be between the carb and the head. Placing the carb close to the head and using a long inlet trumpet has the same effect.


In my opinion only true at WOT
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